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Take Open Channel Flow Measurement and meter total flows
This product is no longer available.  Please see the latest version of this product HERE.

Open Channel Flow Monitor

  • Digital LCD screen
  • Easy-to-use interface with user selectable flow tables
  • Highly accurate depth probe
  • Output signal for recorders or displays
  • Sampler triggering output
  • Water resistant enclosure
To Order Call 1-800-876-1172
Open Channel Flow Monitor Options & Prices


On this page:

Open Channel Flow Monitor Product Description
Open Channel Flow Monitor Specifications
Open Channel Flow Monitor Options & Prices

Downloads (PDF):

Open Channel Flow Monitor Brochure
Open Channel Flow Monitor Manual*

*May take several minutes to download, depending on your internet connection speed.

Additional Information:

Stream Flow Gauging
Inflow and Infiltration information
Product Support

Open Channel Flow Monitor Product Description
Global Water's Open Channel Flow Monitor is reliable and accurate for measuring and totalizing open channel flows for all flumes and weirs, as well as for any gravity-type open-channel flow application.  The flow meter measures water depth with Global Water's highly accurate pressure transducer, and the unit's electronic circuitry instantly calculates and displays water flow and totalizer values for any depth-to-flow relationship in any engineering units.  The Open Channel Flow Monitor is easy to set up in the field using a unique four-button programming system.

Open Channel Flows
For any open channel that is free flowing, there is a specific relationship between depth of water and flow rate.  Whenever a given depth occurs, there will always be the same flow.  Therefore, if the flow rate is known for each depth, a depth-to-flow relationship can be constructed.  The Open Channel Flow Monitor is pre-programmed with depth-to-flow relationship tables.  When the user digitally selects the correct depth-to-flow relationship for an application, the Open Channel Flow Monitor's LCD screen automatically displays accurate flow rate measurements for any depth that is reached.  This water flow is averaged over time to display total flow.

When using a primary device to measure flow, such as a measuring flume or weir, there is a mathematical relationship between depth and flow.  When measuring flow in a channel that does not have a primary device, the depth-to-flow table can be constructed by measuring the flow at several different depths, using Global Water's Flow Probe.

Depth Measurement
Global Water's Open Channel Flow Monitor measures flow depth with the highly-accurate WL400 Water Level Sensor, which is a fully submersible water level sensor constructed of stainless steel.  The standard level range is from 0 to 3' of water, which provides for accurate flow measurements even with a depth change as small as a fraction of an inch.  The pressure transducer is mounted slightly below the "zero" flow depth of the channel, upstream from the throat of the flume or weir.  For open channels with no primary device, the sensor is mounted below the lowest expected water depth.  The water level sensor has a 2-wire 4-20 mA signal, so the flow computer can be mounted several hundred feet away, if required.  The sensor and computer can be connected with standard, twisted-pair signal wire.

Global Water also offers an ultrasonic water level sensor that allows the Open Channel Flow Monitor to measure semi-solid flows or flows that are not suitable for a standard submersible pressure transducer.  Global Water recommends that the ultrasonic sensor option only be used in areas where AC power is available.  You should strongly consider using a submersible pressure transducer for applications that are in areas without AC power.

Display and Outputs
The Open Channel Flow Monitor displays flow rate on a large 6-digit LCD screen.  The totalized output is shown on a second LCD display.  The display reads in user-defined units of flow, including mgd, csf, gpm, m3s.

The Flow Monitor also produces an analog 4-20 mA output signal that is proportional to flow.  This can be used for chart recorders, dataloggers, or as an input to telemetry or process control systems.  In addition, the meter has a flow-proportional output signal for triggering water samplers.

Digital Flow Computer
The Global Water Open Channel Flow Monitor has powerful internal electronic circuitry that calculates and totalizes flow.  Desired engineering units and depth-flow relationships (from over 20 pre-defined tables) can easily be selected using the unit's four front panel push buttons.  User programming does not require the unit's enclosure to be opened.  The unit's manual includes programming information, including depth-to-flow tables for all standard flumes and weirs.

The enclosure is made of weatherproof injection molded plastic.  It is suitable for use in a wide variety of environments.  The enclosure can be wall-mounted and fitted with conduit for sensor and power connections, if required.

Open Channel Flow Monitor Specifications

Rate Display: 6 digit + decimal place, LCD
Totalizer Display: 6 digit + decimal place, LCD
Accuracy: Pressure transducer: +0.2% FS + Flow Monitor: +0.01% + the depth-flow-table error
Flow Units: CFS, GPM, m3s, MGD
Totalizer: Related to Flow Units
Power: 120 VAC to 240 VAC, optional: Battery powered (Must be specified at time of ordering)
Current Draw: 60mA Typical, 100mA max when the output relays are on, and 100uA in sleep mode
Enclosure: 4-3/4x8x3 inch (12x20x7-1/2 cm) (WxHxD), NEMA 4X (IP67)
Weight: 3.4 lbs (1.54 kg)

Pre-defined Tables
Parshall: 1", 2", 3", 6", 9", 12"
Palmer-Bowlus (4D): 4", 6", 8", 10", 12", 15"
Weir: 45° V notch, 90° V notch, 1' rectangular, 2' rectangular
H: 0.4HS, 0.6HS, 0.5H, 0.75H, 1.0H, 1.5H, 2.0H
Trapezoidal: 60°

Custom Table
You must provide Global Water with a depth to flow equation or look up table at time of order.  Please allow for longer lead times.

Open Channel Flow Monitor Sensor
Sensing Element
Sensor Element: Silicone Diaphragm, Wet/Wet Transducer
Pressure Range: 0-3'
Linearity and Hysteresis: ±0.1% FS
Accuracy: ±0.1% of full scale at constant temperature, ±0.2% over 35-70°F (1.37-21.1°C) range
Overpressure: Not to exceed 2 x full scale range
Resolution: Infinitesimal (Analog)
Outputs: 4-20 mA or 0.5 to 2.5 VDC across 125 ohms
Supply Voltage: 8 to 36 VDC
Current Draw: Same as sensor output
Warm Up Time: 3 seconds recommended
Operating Temperature: 0 (not frozen) to +185°F (-17 (not frozen) to +85°C)
Compensation: Uses dynamic temperature compensation 30 to 70°F (-1.1 to 21.1°C).  Automatic barometric pressure compensation
Weight: 1/2 lb (227 g)

Material: 304L Stainless Steel, SS microscreen (hundreds of holes to prevent fouling), electronics are fully encapsulated in marine grade epoxy, guaranteed not to leak
Size: up to 13/16" diameter x 5 1/2" long (2 cm dia. x 14 cm long)(small enough for a 1" well)

Vented Cable
Conductors: 4 each 22 AWG
Material: Marine grade polyether jacket, polyethylene vent tube, full foil shield
Outer Diameter: 0.306 inch (0.78 cm)
Temperature Range: -22° to +185°F (-30° to +85°C)
Weight:0.7 oz/ft (~65g/m)
Length:  Standard 25' (7.62 m) (up to 500' (152.4 m) from factory)

Open Channel Flow Monitor Options & Prices
Prices listed are for United States and Canada only.  Call or e-mail us for pricing in other countries.
Terms and Conditions


FC200 Open Channel Flow Monitor (PN# BH0000)
0-3' Depth Sensor on 25' of cable included.  Please specify flume/weir type when placing order.
FC200-U Open Channel Flow Monitor (PN# BH0400)
0.17' to 1.00' ultrasonic sensor on 10' of cable included (for use with AC power only).  Please specify flume/weir type when placing order.
FC200-D Open Channel Flow Monitor Datalogging Option (PN# BHA000)
0-3' Depth Sensor on 25' of cable included.  Please specify flume/weir type when placing order.  Includes internal GL500S-2-1 serial datalogger.
FCBAT Battery Option (PN# BH0500)
Includes Heavy-Duty Weather Resistant Environmental Enclosure and 12V, 4.5Ah rechargable battery.
PDAGL500 Deluxe PDA Package (PN# AK0500) 
Handheld PDA download package for GL500.
$727 Open Channel Flow Monitor PDA
FC200-S Sewer Flow Monitor
0-3' Depth Sensor on 25' of cable included.  Please specify correct sewer flow table when placing order.
FL16 Water Flow Logger
The Water Flow Logger revolutionizes flow data collection for applications such as inflow & infiltration studies, stormwater and wastewater collection systems, open channels and a host of other gravity flow systems.
Parshall flume
Industry standard rectangular flume used to monitor streams and channels.
Palmer-Bowlus Flume
U shaped channel flume specifically designed for monitoring flows in pipes.
H flume
Used to monitor free fall outflow from pipes or channels when a Palmer-Bowlus or Parshall Flume will not work.
GL500 Open Channel Flow Recorder
Open channel flow recorder for sensor datalogging.  Includes Global Logger Software.  With weather proof enclosure and 12V battery.
$868 Open Channel Flow recorder
FSS-STD Flow Sampling System
A unique combination of products that makes monitoring, sampling, and recording stormwater or industrial discharge water flows easy.
WL700 Ultrasonic Water Level Sensor
Specify Water Level Range: 1', 3', 6'. Includes 10' cable.
FP111 Flow Probe
Water velocity probe for determining open channel flow.
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